On April 19, nine states and six cities filed a brief to the U.S. Supreme Court on an appeals court’s 2012 decision to vacate the Environmental Protection Agency’s (EPA’s) Cross-State Air Pollution Rule. The EPA and several environmental groups appealed the decision to the Supreme Court. The brief said states have the capability to create modeling on air quality; the states also said the decision removed an essential tool for downwind states to comply with the Clean Air Act. The rule required 28 states to reduce emissions to assist other downwind states in meeting air quality standards. The nine states that filed the brief are CT, DE, IL, MD, MA, NY, NC, RI, and VT; Baltimore, Bridgeport, Chicago, the District of Columbia, New York, and Philadelphia were the six cities that signed the brief.